Method and apparatus for discharging static electricity



R. GUNN Dec. 18, 1951 METHOD AND APPARATUS FOR DISCHARGING STATIC ELECTRICITY Original Filed Jan. 4, 1945 Patented Dec. 18, 1951 METHOD AND APPARATUS FOR DISCHARG- ING STATIC ELECTRICITY Ross Gunn, Washington, D. C.

Continuation of application Serial No. 471,252, January 4, 1943. This application January 9, 1948, Serial No. 1,425

4 Claims. (01. 175-264) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 3 70 O. G. 757) This application is a continuation of my application Serial Number 471,252 filed January 4:, 1943,. now abandoned.

This invention relates to a method for con trolling the free electrical charge on an insulated body, and it is particularly directed to a method and apparatus for controlling the free electrical charge on aircraft in flight, to reduce the hazards of lightning when flying near thunderstorms, to reduce the possibility of electrical spark when an aircraft dumps gasoline and to reduce radio interference.

It is well known that aircraft accumulate a free electrical charge when flying through certain rain clouds, snow or near thunderstorms, and that this free charge often becomes high enough to cause corona discharge from the extremities of the craft, such as wing tips and tail surfaces. This discharge causes an almost constant rushing or crying noise known precipitation static in the aircrafts radio receiver, often completely obliterating communication.

This invention provides a method of controlling the free charge on any insulated body, although it is particularly directed to the reduction of the free charge on aircraft in flight and consequent reduction of precipitation static interference to radio communication. Apparatus for accomplishing these objects are herein disclosed.

The method of controlling the free charge on the insulated body comprises, broadly, ejecting charged particles or larger units from the body, the charge on the particles being selected so that the free charge on the body is increased or reduced, whichever is desired. There are several ways this may be done, such as throwing a fine liquid spray into the atmosphere and charging the droplets as they leave the body, as described hereinafter.

If the free charge is to be controlled by ejecting a charged spray into the air, it is accomplished by placing a highly charged electrode near the spray nozzle and slightly to one side of the stream of spray for the purpose of inducing free electric charge on the spray droplets.

In order that the invention may be clearly understood several embodiments thereof are described in detail with reference to the accompanying drawing, in which:

Fig. 1 is a diagram of an apparatus adapted to control the free charge by means of a spray, and

Fig. 2 is a diagram of an apparatus for automatically controlling the potential of an aircraft.

In Fig. 1, an aircraft body 49 is schematically shown with a fine nozzle 45 protruding therethrough into the airstream. A non-insulating liquid, such as water, is pumped through the nozzle M from a reservoir 42 by means of a gear pump 43 and conduit 44. The flow may be controlled by a valve 45. The water is ejected from the nozzle 4| in the form of a very fine spray or mist induced by the airblast. Near the end of the nozzle 4| an electrode 46 is positioned, and it is insulated from the body 4! by an insulator 49. A high potential is applied to the electrode 46 by means of a source of potential 41 and potentiometer 48. As the spray or mist is blown out of the nozzle 4| it becomes charged by induction, due to the influence of the electrostatic field exist ing between the nozzle 4! and the electrode 46. Since the charged spray is swept away by the air flow the aircraft becomes charged with a polarity opposite to that of the spray, which will neutralize or reduce existing free charge if it is of opposite polarity.

By control of the potential on electrode 46, therefore, charge of the aircraft may be varied at rapid rates to bring it to the desired potential. In most cases this will be the potential of the surrounding atmosphere. In other cases, such as in scientific investigations, other potentials may be desired.

Automatic means shown in Fig. 2 for controlling the charge on the electrode 45 may be employed.

Instead of employing a potentiometer to control the charge on the electrode 46, an electronic bridge circuit is employed, the balance of which is controlled by the electrostatic field around the aircraft caused by the free/charge thereon. The circuit comprises a source of potential 24, a vacuum tube 25 having an anode 25a, a cathode 25c and a grid 25g, and a vacuum tube 25 having an anode 25a, a cathode 25c and a grid 26g. The source of potential 24 is connected across the anode 25a and the cathode 250 through an impedance 2?, and across the anode 23a and the cathode 250 through an impedance 28. The anode 26a is grounded to the aircraft body 28, and the anode 25a is connected to the electrode 23 through a microammeter 29. The grids 25g and 25g are connected to the cathodes 25c and 250 through high resistances 30 and 3|, respectively.

It is obvious from the circuit that the polarity of the charge on the electrode 45 depends on which of the tubes 25 or 26 is most conducting. Thus, if the tube 25 is more conducting than the tube 25, current flows through the impedance 2? causing the electrode 46 to become negative with respect to the point 32. Since there is little current flowing through the tube 25, the point 32 is at substantially the same potential as the aircraft body 20 and exhaust pipe 22. Therefore the electrode has a negative charge with respect to the body of the plane 29.

On the other hand,'if the tube 25 is less conducting than the tube 26, the greater current will flow through the impedance 23 and not through the impedance 2'! (except for a negligible space current including that due to ion discharge on the electrode 23), and the point 32 and the electrode 55 will become positive with respect to the aircraft body 20.

In order that the electrode 23 will have the proper polarity to reduce the free charge on the aircraft to a minimum it is necessary to control the potentials of the grids 25g and 225g in accordance with the free charge on the aircraft. This is done by connecting the grids to the terminals of a generating voltmeter 33, such as described in the Gunn U. S. Patent 1,919,215, or any other related electrostatic field sensitive device. The voltmeter 33 comprises two inductors 33a and 3312 connected to a highly insulated split ring commutator 33c and adapted to rotate in the electrostatic field caused by the free charge on the aircraftv The inductors 33a and may be conveniently rotated by an electric motor or other mechanical means. The amount of the charge induced on the inductors 33a and 33b depends on the strength of the electrostatic field surrounding the aircraft (i. e. amount of free charge on the aircraft), its polarity and the position of the inductors during rotation. Thus, as the inductor 33b approaches the body 20 of the aircraft the charge on the latter induces a charge of opposite sign on the inductor 3%. Likewise the inductor 33a. (being connected to the inductor 33b through the impedances 35 and 3!) assumes a charge opposite to that of the inductor 33b because it is simultaneously moving away from the aircraft body 29. Therefore, by means of the commutator 330 the induced charges are converted into a pulsating direct current potential which is applied to the grids 25g and 29g. As the free charge on the aircraft increases, the charge on the electrode 29 also automatically increases so as to reduce the free charge on the aircraft. Similarly, if the free charge on the aircraft reverses polarity, so does the charge on the electrode 56, with the result that at all times the free charge on the aircraft is kept at a minimum.

Many variations will be apparent to those skilled in the art, and the invention should not be limited other than as defined by the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United. States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. Apparatus for varying the potential of an electrode from positive to negative with respect to a body which comprises. an electronic bridge circuit including a plurality of electronic tubes having a cathode, a grid. and an anode, impedances, a source of high potential connected to said cathodes, one anode connected to said body and to said source through one of said impedances, the other anode connected to said electrode and to said source through another of said impedances, means for varying the potential of said grids in opposite phase, thereby to cause one tube to become conducting and the other tube substantially non-conducting and to cause said electrode to become positive or negative by virtue of the potential drop in one of said impedances.

2. A system for controlling aircraft potential comprising liquid reservoir means, nozzle means positioned externall of the aircraft in the slipstream thereof, means for feeding liquid from the reservoir to the nozzle to eject the same as liquid droplet spray from the aircraft into the atmosphere, an inductive control electrode mounted in the slipstream adjacent the nozzle and free of contact with the ejected liquid of the spray stream and means for applying a charge to the control electrode and operative to charge the same with the same polarity as the atmosphere to charge the liquid droplets inductively as ejected.

3. Means for removing static charge from an aircraft comprising an element in electrical contact with the aircraft and adapted to conduct induced static charges therefrom as the same is generated during flight, an inductive control electrode adjacent said element in the slipstream of the aircraft free of contact with said charges and means responsive to the electrical charge of the atmosphere adjacent the aircraft connected to the control electrode and operative to charge the electrode with the same polarity as the atmosphere.

4. In combination with an aircraft of conductive structure, a liquid supply chamber within the aircraft for receiving a non-insulating liquid, conduit means connected therewith terminating in a nozzle electrically connected with the aircraft and positioned to eject a continuous liquid stream in the external air stream of the aircraft, whereby the liquid stream is broken into a spray of fine liquid drops in a breaking zone at the nozzle, an electrode insulated from the aircraft positioned near the nozzle free of contact with the ejected liquid of the spray and operative to establish a controlling inductive electric field in the breaking zone, and means for applying a control potential of selected polarity between the aircraft and the electrode to charge the drops on formation with the opposite polarity.

ROSS GUNN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,205,095 Kelly Nov. 14, 1916 1,252,183 Schmidt et a1. Jan. 1, 1918 1,419,261 Howard June 13, 1922 1,499,425 Chapman Apr. 8, 1924 1,715,202 Lewis May 28, 1929 1,940,700 Riehm Dec. 26, 1933 2,303,321 Bennett Dec. 1, 1942 2,309,584 George Jan. 26, 19 13 2,318,093 Penney May i, 1943 2,320,146 Leake May 25, 1943 2.33.2,144 Bennett et a1 Nov. 2, 1943 2,333,975 Bennett Nov. 9, 1943 2,386,647 Andresen Oct. 9, 1945 

